JPH02158539A - Sheet conveyer - Google Patents

Abstract

PURPOSE:To accurately feed a sheet at a high speed further at a fixed speed by forming a drive roller in its hardness larger than the hardness of a driven roller further the drive roller in a friction coefficient of its surface larger than the friction coefficient of the surface of the driven roller. CONSTITUTION:A drive roller 1 is formed in a friction coefficient of its surface larger than a friction coefficient of the surface of a driven roller 2. Consequently, a sheet 5 is moved following the movement of the drive roller 1. Here the drive roller 1, being formed also in its hardness larger than the hardness of the driven roller 2, obtains a radius R of the drive roller 1 in a fixed value, while the drive roller 1, generating its angular speed omega also in a fixed value, obtains a moving speed also in a fixed value Romega of the sheet 5 when it passes through the roller. As the result, the sheet 5 is conveyed at a fixed speed with no deceleration.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a sheet conveying device used in a conveying system of various sheet processing devices such as copying machines, printers, printing machines, etc. In particular, the present invention relates to a sheet conveying device that is used in a conveying system of various sheet processing devices such as copying machines, printers, printing machines, etc. related to things.

(Prior Art) Conventionally, a sheet conveyance roller pair as shown in FIG. 4 has been used in a conveyance system of a sheet processing apparatus for copying a'5. In FIG. 1, this pair of sheet conveying rollers has a driving roller 101 and a driven roller 102 in contact with each other in a state where they are pressed against each other by applying pressure F by a spring 103. The motor 106 is operatively connected to the motor 106.

Further, as shown in FIG. 5, gears 107 and 108 are interposed between the driving roller 101 and the driven roller 102, so that both rollers are driven.

There is also a pair of sheet conveying rollers that prevents slipping during sheet conveyance.

In such a pair of sheet conveying rollers, the driving roller 101 is rotated by the motor 6 and the driven roller 10 is simultaneously rotated by the motor 6.
2 rotates following the drive roller 101, and the sheet is bitten by this pair of rollers and conveyed.

In this case, the radius size of both the driving roller 101 and the driven roller 102 is R.

If the magnitude of the angular velocity is ω, then the magnitude of the moving speed of the sheet is Rω.
If the hardness of the rollers 2 and 2 is the same, as shown in FIG. 6, the rollers 101 and 102 that are in contact with the sheet 109 are pressed against each other and deformed, and the radius of the rollers changes to R'. The moving speed of the sheet 109 is R'ω. Since the size of R' is unstable, it is difficult to control the sheet feeding speed in this case.Also, since the hardness is the same, both rollers will wear out, so both rollers need to be replaced, which increases the cost. becomes higher. In consideration of this, generally, one roller is made of a highly rigid material such as plastic or fully bent (hereinafter referred to as a rigid roller) so that the driving roller 101 and the driven roller 102 have different hardness. , the other roller is a roller made of a highly elastic material with a rubber cap (hereinafter referred to as an elastic roller).

FIG. 7 is a diagram showing sheet feeding when the driving roller 101 is a rigid roller and the driven roller 102 is an elastic roller. As shown in FIG. Since the sheet 109 rotates and the radius is kept at a constant value R, the moving speed of the sheet 109 becomes a constant value Rω, and the feeding speed can be controlled. Furthermore, the radius of the portion of the driven roller 102 that touches the sheet 41 is R'(R'<R);
Since the deformation is large, see) 109 and rollers 101 and 102.
This increases the contact area with the sheet and stabilizes sheet feeding.

Note that when both rollers are driven as shown in Figure 5, the driven roller also rotates at a constant angular velocity ω, so even if the driven roller is a rigid roller and the driving roller is an elastic roller, the sheet The moving speed becomes a constant value Rω.

In addition, as one of such sheet conveyance roller pairs, the difference in hardness between the rigid roller and the elastic roller is particularly increased to greatly deform the elastic roller, and the curved path formed thereby causes the sheet to have a predetermined curl. - There is a so-called curling roller that is designed to curl. A curling roller like this.

It is used to add a predetermined curl to a sheet, or to remove a curl from the sheet.1 For example, when the sheet moves on the surface of a drum-shaped member such as a photoreceptor drum, the sheet is pre-curled against the drum-shaped member. The sheet is curled to prevent it from wrapping around the drum-shaped member.

(Problems to be Solved by the Invention) Recently, there has been a demand for image recording devices such as Copy A to record images at higher speed and with higher quality.
In sheet conveyance, it is also necessary to feed sheets at high speed and accurately. In particular, if the feeding speed is unstable, the recorded image will shift or stretch, so it is necessary to feed the sheet at a constant speed.
In the pair of sheet conveying rollers described above, the precision of the drive means such as a motor and the transmission system such as gears is increased, and the sheet is accurately conveyed at a constant speed without reducing the speed at which the sheet moves when it passes through the rollers. need to be transported.

However, in general, W! on the surface of the above-mentioned rigid roller! Since the coefficient of restraint is smaller than the coefficient of friction of the surface of the elastic roller, the sheet follows the elastic roller, and since the radius of this elastic roller is unstable, the conveyance speed of the sheet tends to become unstable.

For example, as shown in FIG. 7, when conveying a sheet, the radius R
The elastic roller 102 is deformed and the radius of the contact portion with the sheet 109 becomes R'(R'<R).
When the angular velocity of 2 matches the angular velocity ω of the drive roller 101, the moving speed of the sheet 109 decreases to R'ω. When the driven roller is an elastic roller, as shown in Fig. 4, when the driven roller rotates only by frictional force, the angular velocity of the driven roller is ω' due to the rotational resistance and inertia of the elastic roller. (ω' × ω), the moving speed of the sink further decreases to R'ω', and when the driven roller is driven by a motor as shown in Fig. Due to accuracy errors, etc., the angular velocity of the driven roller is ω (ω″≠ω), and the sheet moving speed is R′
ω''. Since the above R', ω, and ω' are unstable values, the moving speed of the sheet is R'ω.

R'ω' and R'ω'' also have unstable values.

As described above, with the conventional pair of sheet conveying rollers, the moving speed of the sheet, that is, the conveying speed may be slowed down or become unstable, resulting in the dark problem that it is difficult to convey the sheet at high speed and accurately. There was a point.

Moreover, especially in the case of curling rollers, the radius of the elastic roller decreases significantly and is unstable, so the above report was written by WJ. Therefore, in order to manage the conveyance speed of the sheet and to synchronize it with the single image recording apparatus, it is necessary to provide a register roller downstream of the curling roller in the conveyance direction. However, by providing register rollers. There were also disadvantages in that the effect of the curling roller was reduced and the structure became complicated.

The present invention has been made to solve the problems of the prior art described above, and its purpose is to provide a sheet conveying device that can feed sheets at high speed and accurately. .

(Means for solving problems) In order to achieve the above object, the present invention has the following features.

In a sheet conveyance device in which a drive roller rotated by a drive means and a driven roller rotated by the drive roller are arranged in contact with each other in a pressed state, and the sheet is conveyed by biting the pair of rollers. .

The hardness of the drive roller is greater than the hardness of the driven roller, and the ff[coefficient of the surface of the drive roller is larger than the coefficient of friction of the surface of the driven roller.

(Function) In the sheet conveying device of the present invention, since the friction coefficient of the surface of the drive roller is made larger than the friction coefficient of the surface of the driven roller, the sheet moves following the drive roller. At this time, since the hardness of the driving roller is also greater than that of the driven roller, the radius R of the driving roller is a constant value, and the angular velocity ω of the driving roller is also a constant value.

The moving speed of the sheet when passing through the rollers also has a constant value Rω.

Therefore, the sheet is conveyed at a constant speed without being decelerated.

(Example) Next, an example of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing the configuration of a sheet conveying device according to an embodiment of the present invention. In v4, l is a drive roller made of plastic, 2 is a driven roller made of a roller 3 made of rubber with a hardness of 40' and covered with a Teflon thin film 4 with a thickness of several m - 100 lm, and the drive roller The hardness of l is sufficiently greater than the hardness of the driven roller 2, and the hardness of the driving roller l
The coefficient of friction on the surface of the driven roller 2 is also made larger than the coefficient of friction on the surface of the driven roller 2. This sheet conveying roller pair 1.2 is
Similar to the conventional example, the driving roller 1 and the driven roller 2 are pressed against each other and are placed in contact with each other, and the driving roller 1 is connected to a driving means (not shown). has been done.

Further, this pair of sheet conveying rollers is arranged upstream in the feeding direction near the photoreceptor drum 5 in the image recording apparatus, and uses a curved path formed by the deformation of a driven roller 2, which is an elastic roller, to transfer the sheet 5 to the photoreceptor drum. It also plays a role as a curling roller that gives a curling effect to the roller 6.

Then, in the same manner as in the conventional example, the sheet 5 is transferred to the roller pair 1.
2 and is sent out in the direction shown in the figure, and after coming into contact with the photosensitive drum 9 rotating in the direction C in the figure and having an image transferred thereon, it is discharged.

In the sheet conveying roller pair 1゜2 configured in this way, the driving roller l is moved to a position a in the figure by a driving means (not shown).
The driven roller 2 rotates at an angular velocity ω in the direction of
'(R'<R), but the radius of the drive roller l is kept at a constant value H. And 1. Since the coefficient of friction on the surface of the driving roller 1 is larger than the coefficient of friction on the surface of the driven roller 2, even if the driven roller 2 does not follow the driving roller 1 immediately due to rotational resistance or inertia, the sheet 5 will not move against the driven roller 2. It slips on the other hand and moves following the drive roller l. Therefore, changes in the radius of the driven roller 2,
Or due to rotational resistance, inertia, accuracy error of the transmission system, etc.

Regardless of the change in the rotational speed of the driven roller 2, the sheet 5
is fed at a constant speed Rω without decreasing the moving speed. Therefore, it is possible to feed the sheet at high speed and accurately, and high-quality images can be recorded at high speed. In addition, since it is possible to control the sheet feeding speed using the roller pairs 1 and 2, the roller pair 1 and 2
．． 2 also serves as a register roller for synchronizing the formation of a powder image on the photoreceptor drum 6 and the feeding of the sheet, and a register roller is provided between the roller pair 1 and 2 and the photoreceptor drum 6. Since there is no need for a separate provision, the configuration is simplified, and the sheet is prevented from wrapping around the photoreceptor drum 6 due to electrostatic attraction without reducing the curling effect of the roller pair 1.2. After the transfer, the sheet is easily separated from the photoreceptor drum and discharged. For that reason,
This also has the effect of increasing the sheet feeding speed.

In this embodiment, by covering the surface of the driven roller with a thin Teflon film, the coefficient of friction on the surface of the driving roller is 1? ! Although the coefficient of friction on the surface of the driving roller is made larger than the coefficient of friction on the surface of the driven roller using other methods, for example, as shown in FIG. A roller made of rubber with a hardness of about 80° with knurling 7 on the surface is used as the driving roller, and a roller made of rubber with a hardness of about 40° is used as the driven roller, and the coefficient of friction on the surface of the driving roller is determined from that of the driven roller. You can also make the third
As shown in the figure, a roller made of rubber, plastic, metal, etc. may be coated with fine powder 8 of metal or ceramic to increase the coefficient of friction on the surface of the roller, and may also be used as the drive roller. Further, a drive roller that has a large surface friction coefficient by kneading fine powder 8 of metal or ceramic may be used as the drive roller.

(Effects of the Invention) As explained above, by using the sheet conveying device of the present invention, sheets can be accurately fed at high speed and at a constant speed. Therefore, it is possible to record high-quality images with little image displacement or stretching at high speed.

In addition, since the sheet conveyance H21 of the present invention can be used as a curling roller and a register roller, the configuration is simplified, and the sheet can be efficiently curled and the sheet can be easily removed from the drum-shaped member. can be separated into

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the configuration of a sheet conveying device according to an embodiment of the present invention, FIG. 2 is a diagram showing a case in which knurls are provided on the drive roller in the same embodiment, and FIG. 3 is a diagram showing the drive roller in the embodiment. A diagram showing a case in which fine powder is applied to the surface of a roller, FIG. 4 is a sectional view showing JIIX&, an example of a conventional sheet conveying device, and FIG. 5 is a sectional view showing another example of a conventional sheet conveying device. , FIG. 6 is a cross-sectional view illustrating sheet conveyance when the hardness of the drive port and the driven roller are the same, and FIG. 7 is a cross-sectional view illustrating sheet conveyance when the drive roller is a rigid roller and the driven roller is an elastic roller. It is a diagram. Code 1... Drive roller 3... Rubber roller 5... Sheet description 2... Followed roller 4... Thin Teflon 1/2... Photosensitive drum

Claims (1)

[Claims] A drive roller rotated by a drive means and a driven roller rotated following this drive roller are arranged in contact with each other in a pressed state, and the sheet is bitten by this pair of rollers. A sheet conveying device for conveying a sheet, characterized in that the hardness of the drive roller is greater than the hardness of the driven roller, and the friction coefficient of the surface of the drive roller is greater than the friction coefficient of the surface of the driven roller. .